Gas monitoring apparatus

• US 5,198,774 A
• Filed: 03/19/1990
• Issued: 03/30/1993
• Est. Priority Date: 12/17/1987
• Status: Expired due to Fees

• Current Assignee: Daniel M. Thorsen, William J. Williams II
• Original Assignee: Daniel M. Thorsen, William J. Williams II
• Inventors: Thorsen, Daniel M., Williams, William J. II
• Primary Examiner(s): Harvey, Jack B.
• Application Number:
  US07/495,822
• Time in Patent Office: 1,107 Days
• Field of Search: 324/464, 324/468, 324/470, 324/438, 324/459, 73/26, 250/379, 250/382, 250/388
• US Class Current: 324/468
• CPC Class Codes: G01N 27/70 and measuring current or voltage

Abstract

There is disclosed apparatus for monitoring the concentration levels of halogen gas in a gaseous atmosphere as confined in an enclosure over a relatively extended period of time. Such monitoring apparatus includes a sensor including first and second electrodes disposed to define a space therebetween through which the gaseous atmosphere flows and a voltage source for applying a voltage between the first and second electrodes whereby an ionization current flows to the first electrode. A control mechanism illustratively in the form of a programmed microcontroller monitors the ionization current collected by the first electrode as the output signal of the sensor, to determine an increase therein as would be indicative of a halogen leak. Upon determining an increase of the sensor output signal above a predetermined difference, the control mechanism removes the energization from the halogen sensor whereby the ionization current is terminated and the life of the sensor extended. The control mechanism further causes an initial reading of the sensor signal to be taken and to be stored, whereby subsequent sensor readings may be compensated by subtracting the stored value therefrom to provide a compensated output indicative of the increased halogen level with respect to the initial background reading thereof. The relatively small halogen sensor output is amplified by a variable gain amplifier, whose gain setting is automatically set over a large range of sensitivities.

Claims

1. Apparatus for detecting an increase of a selected difference in the concentration of a predetermined gas in a gaseous atmosphere from a first level to a second level thereof, said detecting apparatus comprising:

(a) a sensor including a heater/anode element and a collector/cathode element disposed to define a space therebetween through which said gaseous atmosphere flows;

(b) means coupled to said heater/anode element and said collector/cathode element for applying a voltage therebetween, whereby ionization of said predetermined gas causes a current flow between said heater/anode element and said collector/cathode element of a magnitude proportional to the concentration level of said predetermined gas in said gaseous atmosphere;

(c) first control means coupled to one of said elements for detecting an increase in said ionization current flow by a corresponding amount as would indicate that the concentration level of said predetermined gas has increased by said selected difference to provide a manifestation indicative thereof; and

(d) second control means responsive to said increased current manifestation for controlling said voltage supplying means, whereby its voltage is applied between said heater/anode element and said collector/cathode element is substantially reduced to a magnitude such that said ionization of said predetermined gas and thus said current flow between said collector/cathode element and said heater/anode element are extinguished so that the life of said sensor is extended.

2. The detecting apparatus as claimed in claim 1, wherein there is further included means coupled across said heater/anode element for applying a voltage thereacross to produce a current sufficient to heat said sensor to its operating temperature.

3. The detecting apparatus as claimed in claim 1, wherein there is further included alarm means for providing a manifestation indicative of a valid leak of said predetermined gas, and actuating means responsive to said voltage reduction by said second control means for actuating after a predetermined period of time said voltage applying means to increase said voltage between said heater/anode and collector/cathode elements, whereby said first control means may detect a repeated increase in said ionization current flow in excess of said given difference, said alarm means being responsive to a plurality of said increased current manifestations for providing said valid leak manifestation.

4. The detecting apparatus as claimed in claim 3, wherein said actuating means is also responsive to said manifestation for disabling said first control means.

5. The detecting apparatus as claimed in claim 4, wherein said actuating means causes said voltage applying means to increase said voltage between said heater/anode and collector/cathode elements for a warm-up period, before re-enabling said first control means to detect said ionization current flow, wherein said sensor is permitted to stabilize before said first control means is re-enabled to detect a repeated increase in said ionization current flow.

6. The detecting apparatus as claimed in claim 1 as adapted for detecting a leak of said predetermined gas within said gaseous atmosphere as confined in an enclosure, said leak detecting apparatus further comprising memory means, and means for taking a first reading of said ionization current flow as indicative of a background level of said halogen gas within said enclosure and for storing said first reading in said memory and for taking second readings of said ionization current flows and for non-destructively accessing said memory and subtracting said first reading from each of said second readings to provide a compensated output indicative of any increase of said level of halogen gas above from said background level.

7. The gas monitoring apparatus as claimed in claim 1, wherein there is further included comparison means coupled to said variable gain amplifying means for comparing said amplified output signal with a set reference concentration level and, if said amplified output signal is greater, for providing an indication of a leak of said predetermined gas into said gaseous atmosphere.

8. Apparatus for monitoring a gaseous atmosphere within an enclosure over an extended period of time for an increase in the level of concentration of a predetermined gas within said enclosure, said gas monitoring apparatus comprising:

(a) a sensor exposed to said gaseous atmosphere for providing a signal indicative of the level of concentration of said predetermined gas within said enclosure;

(b) memory means;

(c) first control means for taking an initial reading of said sensor signal as indicative of a background level of the concentration of said predetermined gas within said enclosure and for storing said background level in said memory; and

(d) second control means for thereafter periodically taking current reading of said sensor signal over said extended period of time and for nondestructively accessing said memory means and subtracting said background level from each of said current readings to provide a compensated sensor signal indicative of the current level of concentration of said predetermined gas less said background level thereof.

9. The monitoring apparatus as claimed in claim 8, wherein said memory means comprises a non-volatile memory.

10. The monitoring apparatus as claimed in claim 9, wherein said non-volatile memory comprises an electrically erasable potentiometer.

11. The monitoring apparatus as claimed in claim 8 as adapted for monitoring said gaseous atmosphere for a given increase in the level of the concentration of said predetermined gas as would indicate a valid leak of said predetermined gas within said enclosure in contrast to a spurious indication thereof, wherein there is further included third control means for initially taking a first reading of said compensated sensor signal and thereafter a second reading of said compensated sensor signal and for storing said first and second readings in a second memory means, fourth control means for accessing said second memory means for determining a difference between said stored first and second readings to provide an indication of said measured increase of the concentration level of said predetermined gas, and fifth control means for comparing said measured increase indication with said given increase and, if greater, for providing a warning manifestation indicative of said valid leak of said predetermined gas.

12. Apparatus for monitoring a gaseous atmosphere to detect a wide range of the levels of concentration of a predetermined gas within said gaseous atmosphere as confined in an enclosure, said monitoring apparatus comprising:

(a) a sensor exposed to said gaseous atmosphere for providing a signal indicative of the concentration level of said predetermined gas within said gaseous atmosphere;

(b) means coupled to said sensor for amplifying said sensor signal to output an amplified signal indicative of the halogen gas concentration level, said amplifying means having a variable gain;

(c) means for setting said gain of said amplifying means; and

(d) means coupled to said variable gain amplifying means for determining whether said amplified output signal is greater than a predetermined level and, if so, for causing said gain setting means to decrease said gain of said amplifying means.

13. The gas monitoring apparatus as claimed in claim 12, wherein there is further included means for causing said gain setting means to increase said gain of said amplifying means until said determining means determines that said sensor signal is greater than predetermined level.

14. The gas monitoring apparatus as claimed in claim 12, wherein said setting means variably sets said gain of said amplifying means at a selected one of a plurality of discrete gains.

15. The gas monitoring apparatus as claimed in claim 14, wherein there is further included means for causing said setting means to increase said gain to the next greater discrete gain of said plurality until said determining means determines that said sensor signal is greater than said predetermined level and, thereafter, for causing said gain setting means to set said gain at the next lower discrete gain of said plurality.

16. The gas monitoring apparatus as claimed in claim 12, wherein said sensor provides its signal in analog form, and there is further included an analog to digital converter coupled to receive said analog sensor signal for converting same into a corresponding digital signal, said determining means responsive to said digital signal for determining whether said analog to digital converter has overflowed and, if so, for causing said setting means to decrease said gain of said amplifying means.

17. The gas monitoring apparatus as claimed in claim 12, as adapted to detect an increase in the level of the concentration of said predetermined gas as would indicate a valid leak of said halogen gas as opposed to a spurious indication thereof, wherein said gain setting means increases incrementally said gain until determining means determines that said sensor signal is greater than said predetermined level and for causing said gain setting means to decrease said gain to a determined lower gain, memory means, means for first taking an original value of said determined gain and thereafter current values of said determined gains and for storing said original value of said determined gain in said memory means, means for accessing said memory means for determining a difference between said original value and each of said current values of said determined gains to provide an indication of the measured increase of the concentration level of said predetermined gas, and means for comparing said determined gain difference with a predetermined gain difference and, if greater, for providing a warning indication indicative of said valid leak of said predetermined gas.

18. The gas leak monitoring apparatus as claimed in claim 17, wherein said taking means first takes an original value of said sensor signal and for storing said original value of said sensor signal in said memory means, said comparing means for comparing said determined gain difference with said predetermined gain increase and if equal and said current value of said sensor signal is greater than said original value of said sensor signal, for providing said warning indication of said valid leak of said predetermined gas.

19. Apparatus for monitoring a gaseous atmosphere for a selected increase in the level of the concentration of a predetermined gas within a given enclosure as would indicate a valid leak of said halogen gas in contrast to a spurious indication, said leak monitoring apparatus comprising:

a) a sensor exposed to said gaseous atmosphere for providing an output signal indicative of the concentration of said predetermined gas in said enclosure, to provide a calibrated output signal;

b) means for calibrating said sensor output signal with respect to a background level of the concentration of said predetermined gas in said enclosure, to provide a calibrated output signal;

c) means for periodically taking a reading of said calibrated output signal to provide a series thereof over an extended monitoring period;

d) means for measuring the difference between successive readings of said calibrated output signal;

e) means for variable selecting the magnitude of said selected increase; and

f) means for comparing said measured difference with said selected increase and, if greater, for providing an indication of said valid leak of said predetermined gas into said enclosure.

20. The apparatus of claimed in claim 19, wherein said transmitting means is responsive to said valid leak indication for transmitting said corresponding measured difference with said message to the controller.

21. The monitoring apparatus as claimed in claim 19, wherein there is included means coupled to said sensor for amplifying said sensor output signal, said amplifying means having a variable gain, means for setting said gain of said amplifying means, means for first taking a first value of said set gain corresponding to said background level of said sensor output signal and thereafter second values of said set gain corresponding to each of said current levels of said sensor output signal and for storing said first and second gain values in said memory means, means for accessing said first value and each of said second values of said set gain to provide an indication of said measured difference in the concentration level of said predetermined gain difference with a predetermined gain difference and, if greater, for providing said leak indication, said transmitting means responsive to said leak indication to be enabled for transmitting said determined gain difference with said message to the controller.

22. The monitoring apparatus as claimed in claim 19, wherein said calibrating means comprises a non-volatile memory means actuated at the beginning of said monitoring period for taking an initial reading of said sensor output signal to provide an indication of said background level of the concentration of said predetermined gas within said enclosure and storing same in said non-volatile memory means, and means for non-destructively accessing said non-volatile memory means and subtracting said background level from the current level of said sensor output signal to provide said calibrated output signal.

23. The monitoring apparatus as claimed in claim 19, adapted for transmitting a message indicative of said valid leak indication to a controller disposed remotely of said monitoring apparatus, wherein there is further included means responsive to said indication to be enabled for transmitting said message to the controller.

24. Apparatus for detecting and measuring concentration levels of a predetermined gas within a gaseous atmosphere over an extended continuum, said continuum comprising a plurality of nonoverlapping ranges, said apparatus comprising:

(a) a sensor exposed to said gaseous atmosphere for providing a signal indicative of the concentration level of said predetermined gas within said gaseous atmosphere;

(b) means coupled to said sensor for amplifying said sensor signal to output an amplified output signal indicative of the concentration level of said predetermined gas, said amplified output signal lying between a first lower and a second upper limit, said amplifying means having a plurality of discrete gains corresponding respectively to said plurality of ranges;

(c) means for setting said gain of said amplifying means; and

(d) means coupled to said variable gain amplifying means for determining whether said amplified output signal is greater than said second upper limit and, if so, for causing said gain setting means to decrease said gain of said amplifying means to the next lower discrete gain, whereby said amplified output signal lies between said first and second limits.

25. The gas detecting and measuring apparatus as claimed in claim 24, wherein said amplified output signal is of an analog form, and there is further included means coupled to said amplifying means for receiving and converting said analog output signal into a corresponding digital signal.

26. The gas detecting and measuring apparatus as claimed in claim 24, wherein said gain setting means provides an output signal indicative of said one set discrete gain.

27. The gas detecting and measuring apparatus as claimed in claim 24, wherein said amplified output signal is of an analog form, and there if further included an analog to digital converter for receiving and converting said amplified analog output signal into a corresponding digital output signal, said determining means responsive to said digital output signal for determining whether said analog to digital converter has overflowed and, if so, for causing said gain setting means to set said gain of said amplifying means to the next lower discrete gain.

28. Apparatus for detecting an increase of a selected difference in the concentration of a particular gas in a gaseous atmosphere for a first level to a second level thereof, said detecting apparatus comprising:

(a) a sensor including a heater/anode element and a collector/cathode element disposed to define a space therebetween through which said gaseous atmosphere flows;

(b) first voltage means coupled to said heater/anode element and said collector/cathode element for applying a voltage therebetween to cause a current flow between said elements proportional to the concentration level of said particular gas in said gaseous atmosphere;

(c) first control means coupled to one of said elements for detecting an increase in said ionization current flow by a corresponding amount as would indicate that the concentration level of said particular gas has increased by said selected difference to provide a manifestation indicative thereof;

(d) second control means responsive to said increased current manifestation for controlling said first voltage means, whereby its voltage as applied between said heater/anode element and said collector/cathode element is substantially reduced to a level such that said ionization current therebetween is extinguished so that the life of said sensor is extended; and

(e) second voltage means continuously coupled across said heater/anode element for applying a voltage thereacross to produce a current sufficient to maintain said sensor at its operating temperature.